Process capability modelling offers a method of matching the shape, technological and
cost capabilities of manufacturing equipment to the requirements of components,
singly or as groups. This provides the basis of planning tools useful in the capital
intensive business of the construction of new manufacturing facilities or the reconfiguration
of existing ones. The success of this modelling approach is dependent
upon having an appropriate representation of the design geometry. The representation
must be such that all geometric inquiries raised by the process capability modelling are
either explicitly held within some data representation or alternatively can be derived
algorithmically by reference to a geometric model. The representation must also be
capable of withstanding the rigours of use within the wider context of implementing an
important part of the Computer Aided Design (CAD) I Computer Aided Manufacture
(CAM) interface within a Computer Integrated Manufacturing (CIM) environment.
This paper describes a feature-based representation which uses External Access
Directions (EAD's) as the characterising aspect of geometry which is used in defining a
feature taxonomy. These EAD's become potential machining directions for a collection
of features on a component and are used as an essential link into generative process
planning activities.
The representation has been used in conjunction with process planning and process
capability modelling applications. This paper concentrates on the latter where the
feature representation has been embedded within a proprietary geometric modeller
which has been provided with a purpose-built user interface to reflect the feature
taxonomy. A feature-based component model is created by the geometric modeller
and accessed by functions which enable flexible component grouping and matching to
process capability through the concept of a composite component. Subsequent
process component grouping within the context of particular manufacturing systems
strategies (cellular manufacture, flow-line, etc) ultimately results in functional machine
descriptions and variants.